1. Technical Field
The invention relates generally to drain valves for locomotive diesel engine cooling systems, and more particularly to temperature sensitive drain valves for such cooling systems.
2. Related Prior Art
Locomotive diesel engine cooling systems usually use water and corrosion inhibitors as a heat transfer medium. One of the problems that may be encountered in the operation of such a cooling system is the freezing of coolant in cold weather when the engine of the locomotive is not running. If the coolant freezes, the resulting expansion of the coolant medium can seriously damage the cooling system.
In order to prevent the coolant from freezing, a coolant drain valve is often incorporated in the cooling system. It is known to provide automatically actuating drain valves which operate to open and afford the drainage of coolant from the system when a certain temperature condition is met. For example, it is generally known for such drain valves to be operable when the coolant temperature drops to a temperature somewhat above freezing. For example, it is known for drain valves to open if the coolant temperature falls to approximately 45.degree. F.
The drain valve in a cooling system is typically placed at a low point in the cooling system so that all of the coolant can drain out when the valve is opened. Also, the drain valve is usually located in a position so that the drain valve is exposed to ambient air surrounding the locomotive, so that the coolant temperature in the proximity of the drain valve can reliably be expected to be the coolest in the system.
It is also known to incorporate electrically operable drain valves in a locomotive engine cooling system. Such drain valves depend on the electrical system of the locomotive to provide the energy to open a solenoid or plunger to open and close the valve. For example, it is known to provide a drain valve having an electrically operated solenoid that is connected to a 74 volt DC (74 VDC) line and that draws current from the electrical system to actuate the plunger and to thereby open and close the valve. In such electrical systems, it is known to provide a battery which provides a nominal 74 VDC output.